I am looking for a low cost faraday cage to evaluate whether external stimuli affect anyone with a mental illness, learning disability, or autism . It should only have a charge less than 10 down to 0 hertz; 0 hertz is ideal. I hope someone here has more training than me acquiring these devices because are so important to my research. Has anyone studied this before?
Hi Derek,
generally, you can use any metal container with sufficiently thick walls. The dimensions of possible windows or other openings should be below, say, 1/20 of the shortest wavelength. Thus, if you had to deal with frequencies below 10 Mhz, the passenger space of a car (with metallic roof) would do. If you care about cell phones, bluetooth, etc., the diameter of openings should not exceed about 5 mm.
As to the thickness, the skin depth (resp. penetration depth) depends on the frequency of the incident field, and the conductivity, permittivity, and permeability of the cage material (have a look at "skin depth" in Wikipedia). For example, at 60 Hz, the skin depth of iron is about 1/4 mm. The thickness of the material should be at least 4 or 5 times the skin depth, so iron sheets of 1 to 1.25 mm thickness will shield about 99 % of the field of power lines.
In any case, the metal sheets have to be electrically well connected; it would not do just to place unconnected sheets on the floor, the walls, and the ceiling.
With static fields (0 Hz), you'll get a perfect shielding of electric fields with any electrical conductive material but the shielding of magnetic fields depends on the permeability of the material; it should be a soft ferromagnetic metal like mu-metal. But I guess a whole chamber made of mu-metal would be expensive; and usually, the only static magnetic field is the earth magnetic field which is weak and part of the natural environment.
I guess the least expensive way is to use an existing subterranean room in a building made of steel-reinforced concrete. Possibly, you still had to shield (or switch off) wiring, lamps, etc.
I don't understand the part "... a charge less than 10 ..." in your question. A Faraday cage can be charged but the field of this charge is nearly zero inside the cage, or exactly zero if the cage has no or only small openings.
BTW, the following is not my field of expertise, but I feel it will be hard to separate the effect of EM fields from the effect of the perceptible surrounding. I imagine to be in different moods if you would test or interview me one time in a nice room with windows etc. or even in an open space and another time in a cellar or an iron cabin lit with candles. Probably you'll need something like a wooden cabin without shielding effect but with an interior similar to the cage, for comparable results.
Thank you for your assistance Joerg. You wouldn't happen to know where I might find a suitable Faraday cage and purchase one its okay if you don't. I appreciate your advice regarding my research.
I'm sorry, I never bought or used a Faraday cage myself.
I guess that prefabricated cages are quite expensive; I would have consultations with some experts first before making a decision. A possible source is, for example:
https://hollandshielding.com/Prefabricated-Faraday-cages
but I have had no experience with this provider.
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